Electroless plating is widely employed in various fields including decorating applications where a luxurious and aesthetic appearance is imparted to a resin molded article for an automotive part and the like, electromagnetic shielding, and wiring technology for a printed circuit board, a large scale integrated circuit, and the like. The reason is that electroless plating can produce a film with a uniform thickness regardless of the kind and shape of the substrate by simply immersing the substrate in a plating solution and can produce a metallic plating film also on a nonconductor such as plastic, ceramic, and glass.
Generally, when a metallic plating film is formed on a substrate (an object to be plated) by electroless plating, a pretreatment for electroless plating is carried out so as to increase adhesion between the substrate and the metallic plating film. Specifically, the surface to be treated is roughened and/or hydrophilized by various etching means, followed by sensitization where an adsorbing substance that promotes adsorption of a plating catalyst on the surface to be treated is provided on the surface to be treated and activation where the plating catalyst is allowed to adsorb on the surface to be treated. Typically, sensitization involves immersion of the object to be treated in an acidic solution of stannous chloride to promote deposition of the metal (Sn2+) capable of acting as a reducing agent on the surface to be treated. The sensitized surface to be treated is immersed in an acidic solution of palladium chloride for activation. In this step, the palladium ion in the solution is reduced by the metal that is a reducing agent (tin ion: Sn2+) and deposited on the surface to be treated as an active palladium catalyst nucleus. After this pretreatment, the substrate is immersed in an electroless plating solution to form a metallic plating film on the surface to be treated.
Hyperbranched polymers are classified as dendritic polymers and have intentionally introduced branches, the most prominent feature of which is a large number of terminal groups. If the terminal groups are imparted with reactive functional groups, the polymer has reactive functional groups highly densely and is expected to find use as, for example, a highly sensitive scavenger for functional substances such as catalysts, a sensitive multifunctional cross-linking agent, or a dispersing or coating agent for metals or metal oxides.
For example, an example has been disclosed where a composition containing a hyperbranched polymer having an ammonium group and metal fine particles is used as a reduction catalyst (Patent Document 1).